Migrate data from a MySQL-compatible tenant of OceanBase Database to a MySQL database

You can create a data migration task to migrate existing and incremental business data from a MySQL-compatible tenant of OceanBase Database to a MySQL database through schema migration, full data migration, and incremental synchronization.

Prerequisites

• You have created the source OceanBase instance and tenant. For more information, see Create an instance and Create a tenant.

• You have created the target database.

  • When the cloud vendor is Amazon Cloud: An Aurora MySQL database instance has been created. For more information, see Creating an Aurora MySQL database instance.

  • When the cloud vendor is Huawei Cloud: An RDS for MySQL database instance has been purchased. For more information, see Purchasing a database instance.

  • When the cloud vendor is Google Cloud: A Cloud SQL instance has been created. For more information, see Creating an instance.

  • When the cloud vendor is Alibaba Cloud: An RDS MySQL database instance has been created or a PolarDB MySQL cluster has been purchased.

• You have created dedicated database users for data migration in the source and the target, and granted required privileges to the users. For more information, see User privileges.

Limitations

• Only users with the Project Owner, Project Admin or Data Services Admin roles are allowed to create data migration tasks.

• Limitations on the source database

  Do not perform DDL operations that modify database or table schemas during schema migration or full data migration. Otherwise, the data migration task may be interrupted.

• At present, the data migration service supports Aurora MySQL V2.x and V3.x, Cloud SQL V5.6, V5.7, and V8.0, Huawei Cloud RDS MySQL V5.6, V5.7, and V8.0, MySQL databases V5.6, V5.7, and V8.0, and OceanBase Database (in the MySQL compatible mode) V2.x, V3.x, and V4.x.

• The data migration service supports the migration of only objects whose database name, table name, and column name are ASCII-encoded and do not contain special characters. The special characters are line breaks and . | " ' ` ( ) = ; / &

• The data migration service does not support case sensitivity. In other words, the names are case-insensitive. If the target has databases or tables with the same names (but different cases) as those in the source, an error is returned during the precheck.

• If the target is a database, the data migration service does not support triggers in the target database. If triggers exist in the target database, the data migration may fail.

Considerations

• If the UTF-8 character set is used in the source, we recommend that you use a compatible character set, such as UTF-8 or UTF-16, in the target to avoid garbled characters.

• If the clocks between nodes or between the client and the server are out of synchronization, the latency may be inaccurate during incremental synchronization.

  For example, if the clock is earlier than the standard time, the latency can be negative. If the clock is later than the standard time, the latency can be positive.

• If you modify a unique index at the target when DDL synchronization is disabled, you must restart the data migration task to avoid data inconsistency.

• Check whether the data migration service migrates columns of certain data types, such as DECIMAL, FLOAT, and DATETIME, with the expected precision. If the precision of the target field type is lower than the precision of the source field type, the value with a higher precision may be truncated. This may result in data inconsistency between the source and target fields.

• In a data migration task where the source is an OceanBase database and DDL synchronization is enabled, if a RENAME operation is performed on a table in the source, we recommend that you restart the task to avoid data loss during incremental synchronization.

• A difference between the source and target table schemas may result in data consistency. Some known scenarios are described as follows:

  • When you manually create a table schema in the target, if the data types of any columns are not supported by the data migration service, implicit data type conversion may occur in the target, which causes inconsistent column types between the source and target.

  • If the length of a column in the target is shorter than that in the source, the data of this column is automatically truncated, which causes data inconsistency between the source and target.

• If you select only Incremental Synchronization when you create the data migration task, the data migration service requires that the local incremental logs in the source database be retained for more than 48 hours.

  If you select Full Migration and Incremental Synchronization when you create the data migration task, the data migration service requires that the local incremental logs in the source database be retained for at least 7 days. Otherwise, the data migration task may fail or the data in the source and target databases may be inconsistent because the data migration service cannot obtain incremental logs.

Supported source and target instance types

Data type mappings

Procedure

1. Create a data migration task.

   

   1. Log in to the OceanBase Cloud console.

   2. In the left-side navigation pane, click Data Services > Migrations.

   3. On the Migrations page, click the Migrate Data tab.

   4. On the Migrate Data tab, click New Task in the upper-right corner.

2. In the task name field, enter a custom migration task name.

   We recommend that you use a combination of Chinese characters, numbers, and English letters. The name cannot contain spaces and must be less than 64 characters in length.

3. On the Configure Source & Target page, configure the parameters.

   1. In the Source Profile section, configure the parameters.

      If you want to reference the configurations of an existing data source, click Quick Fill next to Source Profile and select the required data source from the drop-down list. Then, the parameters in the Source Profile section are automatically populated. If you need to save the current configuration as a new data source, click on the Save icon located on the right side of the Quick Fill.

      You can also click Quick Fill > Manage Data Sources, enter Data Sources page to check and manage data sources. You can manage different types of data sources on the Data Sources page. For more information, see Data Source.

      Parameter	Description
      Cloud Vendor	We support these cloud vendors: Amazon Cloud, Huawei Cloud, Google Cloud, and Alibaba Cloud.
      Database Type	The type of the source. Select OceanBase MySQL Compatible.
      Instance Type	Includes Dedicated (Transactional) and Self-managed database. Currently, only migration of data from Dedicated (Transactional) to MySQL database is supported.
      Region	The region of the source database.
      Connection Type	Available connection types are Endpoint and Public IP. If you select Endpoint connection type, you need to first add the account ID displayed on the page to the whitelist of your endpoint service. This allows the endpoint from that account to connect to the endpoint service. For more information, see the corresponding topic under Connect via private network. If you select the Public IP connection type, you must add the data migration IP address displayed on the page to the OceanBase database whitelist. For more information, see the corresponding topic under Connect via public network. Note You need to select the source and target regions before the page displays the data source IP addresses that need to be added to the whitelist.
      Connection Details	When you select Connection Type as Endpoint, enter the endpoint service name. When you select Connection Type as Public IP, enter the IP address and port number of the database host machine.
      Instance	The ID or name of the instance to which the MySQL-compatible tenant of OceanBase Database belongs. You can view the target instance's ID or name on the Instances page. Note When the cloud vendor is Alibaba Cloud, you can also select a cross-account authorized instance of an Alibaba Cloud primary account. For more information, see Alibaba Cloud account authorization.
      Tenant	The ID or name of the MySQL-compatible tenant of OceanBase Database. You can expand the information about the target instance on the Instances page and view the ID or name of the tenant.
      Database Account	The name of the database user in the MySQL-compatible tenant of OceanBase Database for data migration.
      Password	The password of the database user.

      If the instance type is Self-managed Database, configure the parameters in the Advanced Settings section if you need to perform schema migration and incremental synchronization.

      

      • If you need to select Schema Migration or Incremental Synchronization on the Select Type & Objects page, enable the sys Tenant Account and configure the following parameters:

        Parameter	Description
        Sys Account	The name of the sys user. This user is mainly used to read incremental logs and database object structure information from OceanBase Database. Create this user under the sys tenant of the business cluster.
        Password	The password of the sys user.

      • If you need to select Incremental Synchronization on the Select Type & Objects page, enable the OBLogProxy and enter the OBLogProxy connection information.

        Notice

        Enable both the sys Tenant Account and OBLogProxy to perform incremental synchronization.

        The OBLogProxy connection information is the incremental log proxy service of OceanBase Database, which provides real-time incremental project access and management capabilities as a service. It facilitates application access to OceanBase Database incremental logs and meets the need to subscribe to incremental logs in network-isolated environments. The format is OBLogProxy IP:OBLogProxy Port.

   2. In the Target Profile section, configure the parameters.

      If you want to reference the configurations of an existing data source, click Quick Fill next to Target Profile and select the required data source from the drop-down list. Then, the parameters in the Target Profile section are automatically populated. If you need to save the current configuration as a new data source, click on the Save icon located on the right side of the Quick Fill.

      You can also click Quick Fill > Manage Data Sources, enter Data Sources page to check and manage data sources. You can manage different types of data sources on the Data Sources page. For more information, see Data Source.

      Parameter	Description
      Cloud Vendor	Amazon Cloud, Huawei Cloud, Google Cloud, and Alibaba Cloud are supported. You can choose the same cloud vendor as the source, or perform cross-cloud data migration. Notice Cross-cloud vendor data migration is disabled by default. If you need to use this feature, please contact our technical support.
      Database Type	The type of the target. Select MySQL.
      Instance Type	When you select Amazon Cloud as the cloud vendor, the instance types supported are Aurora MySQL, RDS MySQL, and Self-managed MySQL. When you select Huawei Cloud as the cloud vendor, the instance types supported are RDS MySQL and Self-managed MySQL. When you select Google Cloud as the cloud vendor, the instance types supported are Cloud SQL and Self-managed MySQL. When you select Alibaba Cloud as the Cloud Vendor, the supported instance types are RDS MySQL, PolarDB MySQL, and Self-managed MySQL.
      Region	After you select the source region, the target region is automatically populated.
      Connection Type	Available connection types are Endpoint and Public IP. If you select Endpoint connection type, you need to first add the authorized account ID displayed on the page to the whitelist of your endpoint service. This allows the endpoint from that account to connect to the endpoint service. For more information, see Adding private network whitelist. If your Cloud Vendor is Amazon Cloud, when you create an Endpoint Service, if the parameter Acceptance required for endpoint connections is set to Enabled, the data migration service will prompt you to Accept endpoint connection request in the Amazon Cloud console upon first connecting via private connection. When your Cloud Vendor is Google Cloud, add authorized projects to Published Services. After authorization, no manual authorization is needed when you test the data source connection. If you select the Public IP connection type, you must add the data migration IP address to the MySQL database whitelist. For more information, see Add to whitelist. Note You need to select the regions for both the source and target regions before the page displays the data source IP addresses that need to be added to the whitelist.
      Connection Details	When you select Connection Type as Endpoint, enter the endpoint service name.
      Database Account	The name of the MySQL database user created for data migration.
      Password	The password of the database user.

4. Click Test and Continue.

5. On the Select Type & Objects page, configure the parameters.

   1. Select One-way Synchronization for Synchronous Topology.

      Data migration supports One-way Synchronization and Two-way Synchronization. This topic introduces the operation of one-way synchronization. For more information on two-way synchronization, see Configure a two-way synchronization task.

   2. Select the migration type for your data migration task.

      Options of Migration Type are Schema Migration, Full Migration, and Incremental Synchronization.

      Migration type	Description
      Schema migration	If you select this migration type, you must define the mapping between the character sets. The data migration service only copies schemas from the source database to the target database without affecting the schemas in the source. In a task that migrates schemas from a MySQL-compatible tenant of OceanBase Database to a MySQL database, the database that does not exist in the target can be automatically created.
      Full Migration	After the full migration task begins, the data migration service will transfer the existing data from the source database tables to the corresponding tables in the target database.
      Incremental Synchronization	After the incremental synchronization task begins, the data migration service will synchronize the changes (inserts, updates, or deletes) from the source database to the corresponding tables in the target database. Incremental Synchronization includes DML Synchronization and DDL Synchronization. You can select based on your needs. For more information on synchronizing DDL, see Custom DML/DDL configurations.

   3. In the Select Migration Objects section, specify your way to select migration objects.

      You can select migration objects in two ways: Specify Objects and Match by Rule.

   4. In the Select Migration Scope section, select migration objects.

      • If you select Specify Objects, data migration supports Table-level and Database-level. Table-level migration allows you to select one or more tables or views from one or more databases as migration objects. Database-level migration allows you to select an entire database as a migration object. If you select table-level migration for a database, database-level migration is no longer supported for that database. Conversely, if you select database-level migration for a database, table-level migration is no longer supported for that database.

        After selecting Table-level or Database-level, select the objects to be migrated in the left pane and click > to add them to the right pane.

        The data migration service allows you to rename objects, set row filters, and remove a single migration object or all migration objects.

        

        Note

        Take note of the following items when you select Database-level:

        • The right-side pane displays only the database name and does not list all objects in the database.

        • If you have selected DDL Synchronization-Synchronize DDL, newly added tables in the source database can also be synchronized to the target database.

        Operation	Description
        Import Objects	In the list on the right side of the selection area, click Import in the upper right corner. For more information, see Import migration objects.
        Rename an object	The data migration service allows you to rename a migration object. For more information, see Rename a migration object.
        Set row filters	The data migration service allows you to filter rows by using WHERE conditions. For more information, see Use SQL conditions to filter data. You can also view column information about the migration objects in the View Columns section.
        Remove one or all objects	The data migration service allows you to remove one or all migration objects during data mapping. Remove a single migration object In the right-side pane, hover the pointer over the object that you want to remove, and then click Remove. Remove all migration objects In the right-side pane, click Clear All. In the dialog box that appears, click OK to remove all migration objects.

      • If you select Match by Rule, for more information, see Configure database-to-database matching rules.

6. Click Next. On the Migration Options page, configure the parameters.

   • Full migration

     The following parameters will be displayed only if Full Migration is selected on the Select Type & Objects page.

     

     Parameter	Description
     Read Concurrency	This parameter specifies the number of concurrent threads for reading data from the source during full migration. The maximum number of concurrent threads is 512. A high number of concurrent threads may cause high pressure on the source and affect business operations.
     Write Concurrency	This parameter specifies the number of concurrent threads for writing data to the target during full migration. The maximum number of concurrent threads is 512. A high number of concurrent threads may cause high pressure on the target and affect business operations.
     Rate Limiting for Full Migration	You can decide whether to limit the full migration rate based on your needs. If you enable this option, you must also set the RPS (maximum number of data rows that can be migrated to the target per second during full migration) and BPS (maximum amount of data that can be migrated to the target per second during full migration). Note The RPS and BPS values specified here are only for throttling and limiting capabilities. The actual performance of full migration is limited by factors such as the source, target, and instance specifications.
     Handle Non-empty Tables in Target Database	This parameter specifies the strategy for handling records in target table objects. Valid values: Stop Migration and Ignore. If you select Stop Migration, data migration will report an error when target table objects contain data, indicating that migration is not allowed. Please handle the data in the target database before resuming migration. Notice If you click Restore after an error occurs, data migration will ignore this setting and continue to migrate table data. Proceed with caution. If you select Ignore, when target table objects contain data, data migration will adopt the strategy of recording conflicting data in logs and retaining the original data.
     Post-Indexing	This parameter specifies whether to allow index creation to be postponed after full migration is completed. If you select this option, note the following items. Notice Before you select this option, make sure that you have selected both Schema Migration and Full Migration on the Select Migration Type page. Only non-unique key indexes support index creation after migration.

     When post index is allowed, we recommend that you adjust the following business tenant parameters based on the hardware conditions of the OceanBase Database and the current business traffic using a command-line client tool.

     // File memory buffer limit
     ALTER SYSTEM SET _temporary_file_io_area_size = '10' tenant = 'xxx'; 
     // For OceanBase database V4.x, disable throttling
     ALTER SYSTEM SET sys_bkgd_net_percentage = 100;  
     

   • Incremental synchronization

     On the Select Type & Objects page, select One-way Synchronization > Incremental Synchronization to display the following parameters.

     

     Parameter	Description
     Write Concurrency	Specifies target data write concurrency during incremental synchronization. The maximum limit is 512. Excessive concurrency may overload the target system and impact business operations.
     Rate Limiting for Incremental Migration	Enable the incremental migration rate limit based on your needs. If enabled, set the RPS (maximum data limit that can be migrated to the target per second during full migration) and BPS (maxim data limit that can be migrated to the target per second during full migration). Notice The RPS and BPS settings here only serve as rate limiting. The actual performance of full migration is limited by factors such as the source, target, and instance specification.
     Incremental Synchronization Start Timestamp	If Full Migration has been selected when choosing the migration type, this parameter will not be displayed. If Full Migration has not been selected when choosing the migration type, but Incremental Synchronization has been selected, please specify here the data to be migrated after a certain timestamp. The default is the current system time. For more information, see Set incremental synchronization timestamp. Note This parameter is only displayed when modifying the parameters of a two-way synchronization task.

7. Click Next to proceed to the pre-check stage for the data migration task.

   During the precheck, the data migration service checks the read and write privileges of the database user and the network connection of the database. A data migration task can be started only after it passes all check items. If an error is returned during the precheck, you can perform the following operations:

   • You can identify and troubleshoot the problem and then perform the precheck again.

   • You can also click Skip in the Actions column of a failed precheck item. In the dialog box that appears, you can view the prompt for the consequences of the operation and click OK.

8. After the pre-check succeeds, click Purchase to go to the Purchase Data Migration Instance page.

   After the purchase succeeds, you can start the data migration task. For more information about how to purchase a data migration instance, see Purchase a data migration instance. If you do not need to purchase a data migration instance at this time, click Save to go to the details page of the data migration task. You can manually purchase a data migration instance later as needed.

   You can click Configure Validation Task in the upper-right corner of the details page to compare the data differences between the source database and the target database. For more information, see Create a data validation task.

   The data migration service allows you to modify the migration objects when the task is running. For more information, see View and modify migration objects. After the data migration task is started, it is executed based on the selected migration types. For more information, see the "View migration details" section in View details of a data migration task.